Q:
Does Saturn's magnetic poles alternate over time? Is Chandra capable of detecting such a transition?

A:
It is a good idea, that the reason for the lack of X-ray "hot
spots" on the magnetic poles of Saturn is due to a changing of polarity
in the magnetic field of the planet. But it seems that Saturn does
have a magnetic north and south pole and so the reason for the lack of
X-rays on the south pole is a mystery.

So, the answer is, it is a mystery! Hopefully Chandra will help solve
it some day. It may be that the magnetic fields are getting slowly
weaker, as the Earth's are, but it seems they are not weak enough to
explain the lack of emission. Please stay tuned to the Chandra
web pages since we have just completed a long observation of the Earth,
and if the Earth does not show hot spots then your idea might be right.
We'd have to find out the difference in magnetic field strength
between Saturn and the Earth to check on this.